Rafter gauging device



" Mmh 12, 1940. y

E. F. CONNORS RAFTER GAUGING DEVICE Filed .July 5, 1939 I5 Sheets-Sheet 1 March 12, 1940. E E CONNGRS 2,193,313

RAFTER c-AUGING DEVICE throw March 12, 1940. E. F. ccaNNoRsY RAFTER GAUGrINCrl DEVICE Filed July 5. 19:59 s sheets-sheet s Patented Mar. 12, 1940 unirse STATES PATENT OFFICE:

This invention relates to a device for 1 solving problems encountered in construction Work, particularly in the building of roof structures, which device is compact and capable of being yused by persons unfamiliar with trigonometric functions.

The calculations of plumb and seat cuts for rafters present diiliculties to the carpenter who is unskilled in mathematics and these difficulties are of particularly great importance in connection with such additional angles as those required for the side cuts of hip jacks, valley jacks, rafters `and the face cuts for sheathing and roong boards. This invention contemplates the provision of a simple and convenient device which will` develop the angles needed for all cuts nort `mally encountered in roong construction `and provide a means for marking those angles directly on the rafters or sheathing boards to be cut.

It is further contemplated that the `device shall be capable of providing the data necessary for` laying out plate forms and the like in the construction of circular and other similar types of roof construction.

Other objects and advantages of this invention will be apparent from the following detailed discussion of the device when considered in connection with the annexed drawings, wherein:

Figure 1 is a perspective View of the complete device in operative adjustment; V

Figure 2 is a plan View of the board forming the base of the instrument position and nature ofindicia engraved in the face thereof;

Figure 3 is a plan view of the tangent leg showing the relation of the indicia indicated on that member;

Figure 4 is a side elevation of the board lassembly shown in Figure 1;

Figure 5 is a section on line V5--5 of Figure 1;

arm; i l

Figure 7 is alplan view of the secant arm illustrated in Figure 6 showingthe sine arm aixed thereto; i

Figure 8 isa-partial section through one end Of the board showing the manner in which the tangent leg is adjusted; t Figure 9 -is a detailed view in elevation of the adjusting means shown in Figure 8 ;V `and Figure 10 is a fragmentary view of a portion `0f the face of the board illustrating the manner in which angular position of the secant arm is designated on a graduated arc.

With particular referenceltoFigure l it will be seen that the device of this. invention comeasily readable.

and showing the Figure 6 is a perspective view of the secant s claims. (c1. as snf prisesa board ID having a tangent leg II, a secantarm I2 and a sine arm I3 mounted thereon for movement with relation thereto in a predetermined manner. Preferably the secant arm is` pivoted near one corner of the board at a` point I4` one inch in from each of the edges forming the corner adjacent thereto. On the face of the board and about the. point I l there is described a graduated arc I5 and a notch l5 is out' in one side of the secant arm in order that readings may be made on thearc I5. The sine arm I3 is pivotally attached to the secant arm I2` at a point I'I beyond the said notch i6. The 'secant arm I2 is provided with a reading edge I8 and it will be noted that the pivot points I4 and Il lie along the line of the said reading edge '|8. It will also be noted that the notch lli is so formed that thereading edge i8 makes a v point therewith to render the graduated aro i5 Graduations along opposite sides of the sine arm give Ithe sine of the angle made by the secant arm with the base and values proportional to the chord of a building when the sine arm is placedperpendicular to the base (denoted here as RRedge). The chord `scale is graduated at `values equal to one-half those employed on the sine scale, in order that the total chord of a building maybe calculated directly in the manner hereinafter disclosed. Disposed within the graduated arc I5 are a number of indicia showing suitable positions for the secant for various cuts to be made in preparing rafters and other rpartsof the building. For rapidity and acouracy, however, the secant arm I8 is preferably adjustedto'the desired position by orientation Withresp'ec gent leg. The tangent leg II is mounted by any suitable means to bemaintained parallel with, and moved with respect to, that edge of the board designated as the R edge. Marked on the face of the t to markings on the face of the tan- -board are indicia of the same general nature as those within the graduated arc l5 to designate .suitable positions onthe tangent-leg il. For

convenience of reading, the markings indicating positions ofthe tangent leg should be large and it is, therefore, preferred that two series of `such markings be employed and provide two dierent graduations on the tangent leg at opposite edges thereof;` Arrows such as I9 are provided on the face of the board to designate the line to Which the tangent leg should be adjusted in using theboard. `LThe tangent leg is set with that edge thereof 'along` the indicated line which will leave the desired indicia in full view. On opposite sides of the tangent leg notches are provided in order that the said leg may be accurately adjusted to position. In a preferred embodiment the tangent leg moves along an upturned edge ZI of the board fitted with holes 22. Each of the said holes 22 is so positioned that it will positively retain the tangent leg II, in one of the several operative positions When a pin 23 is thrust through the said hole 22 and corresponding holes in portions of the tangent leg overlapping the edge 2I. A collar i4 cooperating With a spring guard 25 prevents the pin 23 from being accidentally dislodged.

It will be understood that the ventire board, including each of the several parts attached thereto, is formed to scale in order that the various graduations marked on 'the'. parts thereof may be useful in making calculations. The rise of arc scale and cosine Scale along the RR edge of the board are preferably drawn to full scale as is the sine scale on the sine arm I3. The "rise of arc and cosine scales are offset in the manner shown from the point Il in order that the same may be accurately read from the edges of the sine arm. In the embodiment here shown, the graduated scales are six inches in length. Likewise, the distance between the centers of pivot points ill and Il' is six inches.

In setting the secant arm by use of the scales on the tangent leg; the tangent leg II is positioned with one edge thereof lying on a line corresponding to the type of cut to be made and the reading edge I8 of the secant arm I2 is positioned to intersect the said edge of the tangent leg l I at the line corresponding to the pitch cmployed in the construction job under consideration. Vlhen the secant arm is positioned in this Vmalmer (or placed in a suitable position by orlentation with respect to the indicia inside the graduated arc I5) an extension 26 of the secant arm I3 underneath the board Will lie with its edges parallel to the reading edge I8. In this position the board forms an accurate and rapid means for marking the angles to be cut directly on the lumber. For example, to make the plumb and seat cuts of a common rafter the secant arm is positioned in suitable relation to the board by the use of either the tangent leg or the indica ineide the graduated arc I and the board is then placed on the timber with the extension 26 lying along one side of the said lumber. The plumb and seat cuts may then be marked along the R edge and RR, edge as designated on the face of the board.

Calculations of the length of the various rafters employed in roof construction have heretofore presented considerable difficulty in the art. The construction of the present device renders it possible to materially simplify this problem. At any given setting for the tangent leg and secant arm there will. appear a number similar to that indicated at El, which number is the, proper multiplier for determining the length of the rafter. The number similar to that indicated at 21 is multiplied by one-half the Widthof the building or by the figure corresponding thereto which is equal to the horizontal distance between the lower and upper end of the rafter, to obtain the correct total length of the rafter. For example, at the position for side cut of a jack rafter, the decimal ligure appears on the indicia along the right hand side of the secant arm coincident with the mark indicating the pitch. This figure is multiplied by the spacing of the jacks on centers in inches rand gives the length of the first jack in inches. In the usual type of construction the next jack is double the length of the first and the following jacks are also simple functions of the length of the first rafter. In this manner, any spacing of the jacks may be used on any Width building to keep them equal distances apart and this method is of particular value in the construction of Octagon and hexagon roofs.

An important advantage of the present invention is the provision of means for laying out circular plate forms- For this use the secant arm is set on the graduated arc I5 at the angle corresponding to the apex angle of the desired plate form segment. The sine arm is then swung perpendicular to the RR edge and the chord reading obtained. The chord reading multiplied by the diameter of the desired form gives the length of chord.

The novel device of this invention is capable of an extremely large number of uses in a cornparatively simple manner even in the hands of one unfamiliar with the use of trigonometric functions. Further consideration of the foregoing discussion by one familiar with problems encountered in construction work Will reveal a large number of manipulations resulting in valuable uses for the device. A few of those uses have been here set out as illustrative of the utility of the invention and it is to be understood that the present disclosure is made With the View to aiding others to understand the device and the manner of its use.

I claim:

l. In a device of the class described, a board, a secant arm extending across the face of said board and having a reading edge lying in a straight line, said secant arm being pivotally attached to said board adjacent one corner thereof at a point in the line of said reading edge and` having means rigidly fixed to said secant arm to define a straight line across the reverse of said board parallel to said reading edge, a sine arm pivotally connected to said secant arm at a point in the line of said reading edge, a tangent leg,

means at a side of the board opposite the corner at which said secant arm is connected to said board to guide said tangent leg across said board while retaining said tangent leg perpendicular to said side, indicia on the face of said board to designate positions of said tangent leg for making various types of lumber cuts involved in roof construction and indicia on the face of said tangent leg to designate settings of the said secant arm determined by pitch of a roof.

2. In a device of the class described, a board, a secant arm extending across the face of said board and having a reading edge lying in a straight line, said secant arm being pivotally attached to said board adjacent one corner thereof at a point in the line of said reading edge and having means rigidly xed to said secant arm to define a Straight line across the reverse of said board parallel to said reading edge, a sine arm pivotally-connected to said secant arm at a point in the line of said reading edge, a tangent leg, means at a side of the board. opposite the corner at which said secant arm is connected to said board to Yguide said tangent leg across said board While retaining said tangent leg perpendicular to said side, indicia on the face of said board to designate positions of said tangent leg for making various types of lumber cuts involved in roof construction and indicia on each of the opposite edgesof said tangent leg todesignate settings of the said secant arm determined by pitch of a roof.

3. In a device of the class described, a board, a secant arm extending across the face of said board and having a reading edge lying in a straight line, said secant arm being pivotally attached to said board adjacent one cornet." thereof at a point in the line of said reading edge and having means rigidly fixed to said secant arm to denne a straight line across the reverse of said board parallel to said reading edge, a sine arm pivotally connected to said secant arm at a point in the line of said reading edge, a tangent leg, means at a side of the board opposite the corner at which said secant arm is connected to said board to guide said tangent leg across said board while retaining said tangent leg perpendicular to said side, indicia on said sine arm denoting values proportional to the sine of the angle defined by said secant arin and a line perpendicular to said tangent leg through said point at which said secant arm is pivotally attached to said board, indicia on the face of said board to designate positions of said tangent leg for making various types of lumber cuts involved in roof construction and indicia on the face of said tangent leg to designate settings of the said secant arm determined by pitch of a roof.

4. In a device of the class described, a board,

a secant arm extending across the face of said board and a reading edge lying in a straight line, said secant arm being pivotally attached to said board adjacent one corner thereof at a point in the line of said reading edge and having means rigidly fixed to said secant arm to denne a straight line across the reverse of said board parallel to said reading edge, a sine arm pivotally connected to said secant arm at a point in the line of said reading edge, a tangent leg, means at a side of the board opposite the corner at Which said secant arm is connected to said board to guide said tangent leg across said board While retaining said tangent leg perpendicular to said side, indicia on the face of said board along the side of said board oppositethat side of the board having means to permit motion of said tangent leg, said indicia cooperating With said sine arm to denote cosine and rise of arc of the angle deiined by said secant arm and a line perpendicular to said tangent leg, indicia on the face of said board to designate positions of said tangent leg for making Various types of lumber cuts involved in roof construction and indicia on the face of `said tangent leg to designate settings of the said secant arm determined by pitch of a 5. In a device of the class described, a board, a secant arm extending across the face of said board and a reading edge lying in a straight line, said secant arm being pivotally attached to said board adjacent one corner thereof at a point in the line of said reading edge and having means rigidly iixed to said secant arm to dene a straight line across the reverse of said board parallel to said reading edge, a sine arm pivotally connected to said secant arm at a point in the line oi said reading edge, a tangent leg, means at a side of the board opposite the corner at which said secant arm is connected to said board to guide said tangent leg across said board While retaining said tangent leg perpendicular to said` side, a graduated arc on the faceof said board about the point at which said secant arm is pivotally attached to said board, means on said secant arm to designate the portion of said arc underlying said reading edge, indicia on the face of said board to designate positions of said tangent leg for making various types of lumber cuts involved in roof construction and indicia on thelace of said tangent leg to designate set-r tings of the saidfsecant arm pitch of a roof.

6. In a device of the class described, a board, a secant arm extending across the face of said board having a reading edge lying in a straight line, said secant arm being pivotally attached determined by to said board adjacent one corner thereof at a` point in the line of said reading edge and having means rigidly fixed tofsaid secant arm to dene a straight line across the reverse of said board parallel to said reading edge, a tangent leg, means at a side of the board opposite the corner at which said secant arm is connected to said board to guide said tangent leg across said board while retaining said tangent leg perpendicular to said side, indicia on the base of said board to designate positions of said tangent leg for making various types of lumber cuts involved in roof construction and indicia on the face of said tangent leg to designate settings of the said secant arm determined by pitch of a roof.

EDWARD F. CONN ORS. 

